Characterization of Properties and Estimation of Power Generation Potentials of Residues of Some Woody Biomass Species

Abstract

In view of continuous increase in energy demand, and the environmental and economic concerns associated with the use of conventional fuels have made scientists and technocrats to look for alternative renewable energy sources for power production. The inherent advantages of carbon neutrality, lower ash content, lower SOx and NOx emissions, and wide availability have made biomass as a prime source of power generation. In this article, three different components taken from residues of five different woody plant species have been considered which have no commercial use. These plant species are Ficus benghalensis (local name- Banyan), Azadirachta indica (local name- Neem), Ficus religiosa (local name- Pippal), Madhuca longifolia (local name- Mahua) and Eucalyptus globulus (local name- Eucalyptus). Proximate analyses and gross calorific values (GCV) of all the biomass species including a coal sample have been determined. Among all the five biomass species studied, the fixed carbon content (FC) in Neem bark was observed to be the highest while its leaf has the lowest value, the volatile matter content (VM) in both Mahua branch and Eucalyptus leaf is the highest while Pippal bark has the lowest and the ash content (A) in bark of Mahua is the highest while the leaf of Eucalyptus biomass species has the lowest ash content. Similarly, the leaf of Eucalyptus is the most suitable one with the highest calorific value followed by leaves of Pippal and Mahua. Next in the order, the barks of Banyan and Neem, and the branches of Pippal, Mahua and Eucalyptus were also found to have considerably high amount of energy contents suitable for power generation. In addition, bulk densities of all the biomass species including the coal sample have been determined. Leaves of all the biomass species have been found to have lower bulk densities as compared to their barks and branches. It is worthy to note that among all the studied biomass species, branch of Eucalyptus has the highest bulk density while leaf of Neem has the lowest. Further, the ash fusion temperatures of some selected components of Banyan, Neem, Pippal and Mahua Page | XII
biomass have been measured as these temperatures are the influential factors for the determination of bed agglomeration and other boiler fouling related problems. The results showed comparatively higher values of softening temperature ST (1077-1329 0C) and hemispherical temperature HT (1193-1450 0C) indicating safe boiler operation. Leaf and branch of Pippal and leaf and bark of Mahua were separately mixed with coal sample in different ratios, and their various percentage compositions related to proximate analyses and energy values were determined to explore the best coal-biomass mixture for power generation. It is evident from the results that the ash content decreased and volatile matter increased when the biomass percentage increased in the coal-biomass blend. The ultimate analysis has also been carried out on selected biomass species of Banyan, Mahua and Pippal. Carbon and Hydrogen contents of both Pippal and Mahua leaf were found to be higher and their corresponding calorific values were also high. The variation in energy values of plant components is undoubtedly related to the combined effects of their C and H contents. As the calorific value is the most salient property of any fuel, including biomass fuel, an attempt has been made to derive numerous regression equations using proximate and ultimate analysis data for prediction of gross calorific values of studied biomass species. The equations have been obtained statistically using regression analysis. The two linear regression equations with the best results obtained on the basis of proximate and ultimate analyses are GCV = – 49.02 + 0.968×FC + 0.719×VM + 0.459×A and GCV = 9.8 + 0.0613×O – 1.44×N – 0.829×C + 8.18×H respectively. The two nonlinear regression equations with best results obtained are GCV = 237.85 – 8.278×M – 5.723×VM – 3.098×FC – 0.055×M2 + 0.129M×VM + 0.089×M×FC + 0.0319×VM2 + 0.061×VM×FC – 0.021×FC2 and GCV = 70.408 + 0.153×O – 3.115×C + 1.035×H – 0.041×O2 + 0.101×O×C – 0.069×O×H – 0.0317×C2 + 1.217×H2 respectively. The results regarding computation of land requirement show that around 84, 618, 254, 148 and 289 hectares of land area are needed for energy plantation considering
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Banyan, Neem, Pippal, Mahua and Eucalyptus biomass species respectively. The above calculation serves the purpose of electricity generation of 7300 MWh per year for a cluster of 10-15 villages on decentralized power generation mode. Further, the requirements of blends of coal-Pippal branch and coal-Mahua bark to generate 7300 MWh/year of electricity was calculated and it was observed that the requirement of coal decreases with increase in the percentage of biomass in these blends. In case of coal-Pippal branch blend, the requirement of coal decreased from 5798 t/year to 5038 t/year and in coal-Mahua bark blend, coal requirement reduced from 5798 t/year to 5076 t/year as both biomass contents increased from 0 to 15%.